#include <bits/stdc++.h>
using namespace std;

string s;
double arr[3];
void get_it() {
    string tmp;
    for (int i = 0, j = 0; i < s.size(); ++i) {
        if (s[i] == ',') {
            arr[j++] = stod(tmp);
            tmp.clear();
        } else
            tmp += s[i];
    }
    arr[2] = stod(tmp);
}

int main() {
    cin >> s;
    get_it();
    printf("%.2f", (arr[2] * arr[2] / 4 * 3.14) / (arr[0] * arr[1]) * 100.00);
    cout << '%' << endl;
    return 0;
}